Compensation procedure for excess transmission opportunity time

ABSTRACT

Methods, systems, and devices are described for efficient use of transmit opportunities (TXOPs) through adjustment of contention window backoff time values to compensate for one or more TXOPs that may exceed a TXOP limit. A contention window value may be increased, for example, to provide other devices in the network with a fair opportunity for network access based at least in part on one or more TXOPs that exceed the TXOP limit. Allowing one or more transmissions to exceed a TXOP limit may provide enhanced efficiency as compared to having multiple transmissions.

CROSS REFERENCES

The present application for patent claims priority to U.S. ProvisionalPatent Application No. 61/943,767 by Wentink, entitled “CompensationProcedure For Excess TXOP Time,” filed Feb. 24, 2014, and U.S.Provisional Patent Application No. 62/010,343 by Wentink, entitled“Compensation Procedure For Excess TXOP Time,” filed Jun. 10, 2014,assigned to the assignee hereof, and expressly incorporated by referenceherein.

BACKGROUND

1. Field of the Disclosure

The following relates generally to wireless communication, and morespecifically to compensating for utilized transmission times relative toa transmission opportunity (TXOP) limit.

2. Description of Related Art

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be multiple-accesssystems capable of supporting communication with multiple users bysharing the available system resources (e.g., time, frequency, andpower). Examples of such multiple-access systems include code-divisionmultiple access (CDMA) systems, time-division multiple access (TDMA)systems, frequency-division multiple access (FDMA) systems, andorthogonal frequency-division multiple access (OFDMA) systems.

A wireless communications network may include a number of networkdevices such as access points (APs) that can support communication for anumber of wireless devices. A wireless device may communicate with anetwork device bi-directionally. For example, in a wireless local areanetwork (WLAN), a station (STA) may communicate with an associated APvia downlink and uplink. The downlink (or forward link) refers to thecommunication link from the AP to the station, and the uplink (orreverse link) refers to the communication link from the station to theAP.

In WLANs, there may be cases in which multiple STAs are in communicationwith a particular AP. Access to the wireless medium may be controlledthrough a medium access control (MAC), which may allow different STAs toaccess a wireless channel according to enhanced distributed channelaccess (EDCA) rules. Included in the EDCA rules is a transmitopportunity (TXOP) limit, which is a duration of time during which a STAis allowed to continually access the medium without backoff. A wirelessnetwork may have multiple different access priorities according to anaccess class of data that is transmitted using the wireless channel,each of which may have a different TXOP limit.

In order to enhance utilization of the wireless network, it may bedesirable for different wireless devices accessing the wireless networkto utilize relatively fewer TXOPs that each contain more transmitteddata rather than relatively more TXOPs that each contain lesstransmitted data. For example, exceeding a TXOP limit may improve theefficiency when sounding or protection overhead needs to be amortized ina TXOP. Furthermore, in some cases, a TXOP limit may be set to zero forcertain types of transmissions (e.g., Best Effort transmission prioritytransmissions), which implies that a single data transmission can takeplace. However, for low physical (PHY) layer data rates (such as 1Mbps), this may cause relatively long transmissions, hence enhancedefficiency may be desirable in such cases.

SUMMARY

Various methods, systems, devices, and apparatuses are described forenhanced network utilization in a wireless communications system throughefficient transmissions of information between an AP and a station. Fairand efficient use of transmit opportunities (TXOPs) may be enhancedthrough adjustment of contention window (CW) backoff time values tocompensate for one or more TXOPs that may exceed a TXOP limit that isset by the network. A CW value may be increased, for example, to provideother devices in the network with a fair opportunity for network accessbased at least in part on one or more TXOPs that exceed the TXOP limit.Allowing one or more transmissions to exceed a TXOP limit may provideenhanced efficiency as compared to having multiple transmissions, eachwith related overhead, that are each within the TXOP limit.

Compensation may be achieved at a station in a wireless communicationsnetwork, according to certain examples, through determination of autilization of a transmit opportunity (TXOP), and determination of adifference between the utilization of the TXOP and a TXOP limit. Thedifference between the utilization of the TXOP and TXOP limit may beaggregated with an accumulated difference between at least one TXOP andthe TXOP limit. Based at least in part on the accumulated difference, acontention window (CW) value may be adjusted for a subsequenttransmission from the wireless communication device. The accumulateddifference may then be adjusted based at least in part on the adjustedCW value. Less than fully utilized TXOPs may be used to compensate forlater TXOPs that may exceed the TXOP limit. Compensation of CW valuesmay be through linear or exponential compensation, according to variousexamples.

A first method for wireless communications may include determining autilization of a transmit opportunity (TXOP) for a transmission of datafrom a wireless communication device; determining a difference betweenthe utilization of the TXOP and a TXOP limit; and aggregating thedifference with an accumulated difference between at least one otherTXOP and a TXOP limit for the other TXOP. The method may also includeadjusting a contention window (CW) value for a subsequent transmissionfrom the wireless communication device based at least in part on theaccumulated difference. The method may also include, in some examples,updating the accumulated difference based at least in part on theadjusted CW value. Adjusting the CW value may include, for example,determining a relative excess between the accumulated difference and aminimum CW value, or scaling the minimum CW value based at least in parton the relative excess. Additionally or alternatively, the method mayinclude determining a second utilization of a subsequent TXOP during asubsequent transmission of data from the wireless communication device;determining a second difference between the second utilization of thesubsequent TXOP and the TXOP limit; and secondly aggregating the seconddifference with the accumulated difference.

A second method for wireless communications may include determining anaccumulated difference between a utilization of one or more transmitopportunities (TXOPs) for a transmission of data from a wirelesscommunication device and a TXOP limit; adjusting a contention window(CW) value for a subsequent transmission from the wireless communicationdevice based at least in part on the determining; and updating theaccumulated difference based at least in part on the adjusted CW value.Adjusting the CW value may include determining a relative excess betweenthe accumulated difference and a minimum CW value; and adjusting the CWvalue based at least in part on the relative excess.

Adjusting the CW value may include exponentially increasing the CW valuewhen the relative excess is greater than a predetermined value, whichmay correspond, for example, to an integer multiple of the TXOP limit.Exponentially increasing the CW value comprises increasing the CW valueby an exponential factor that is based at least in part on the integermultiple. Adjusting the CW value may include linearly increasing the CWvalue when the relative excess is greater than a predetermined value.Linearly increasing the CW value may include, for example, multiplyingthe relative excess by the minimum CW value; and rounding down to a nextinteger CW value.

Adjusting the CW value may include decreasing the CW value when theaccumulated difference is less than a predetermined value. Thepredetermined value may be determined, for example, based at least inpart on a ratio of the accumulated difference and the TXOP limit.Decreasing the CW value may include, for example, multiplying the ratioby a minimum CW value; and rounding down to a next integer CW value.Adjusting the CW value may include increasing the CW value to allow forincreased utilization of a subsequent TXOP relative to the TXOP limit.

A third method for wireless communications may include determining autilization of a transmit opportunity (TXOP) for a transmission of datafrom a wireless communication device; determining a difference betweenthe utilization of the TXOP and a TXOP limit; aggregating the differencewith an accumulated difference between at least one other TXOP and aTXOP limit for the other TXOP; and setting initial contention windows(CWs) such that a ratio between an average CW and an average sum of theTXOP limit and the accumulated difference equals a ratio between aminimum CW and the TXOP limit.

An apparatus for wireless communications may include a utilizationmonitor configured to determine a utilization of a transmit opportunity(TXOP) for a transmission of data from a wireless communication deviceand determine a difference between the utilization of the TXOP and aTXOP limit; and an aggregator configured to aggregate the differencewith an accumulated difference between at least one other TXOP and aTXOP limit for the other TXOP.

The apparatus may implement one or more aspects of the first, second, orthird methods described above.

An apparatus for wireless communications may include a utilizationmonitor configured to determine an accumulated difference between autilization of one or more transmit opportunities (TXOPs) for atransmission of data from a wireless communication device and a TXOPlimit; a contention window (CW) adjuster configured to adjust a CW valuefor a subsequent transmission from the wireless communication devicebased at least in part on the determining; and an update unit configuredto update the accumulated difference based at least in part on theadjusted CW value.

The apparatus may implement one or more aspects of the first, second, orthird methods described above.

An apparatus for wireless communications may include a utilizationmonitor configured to determine an accumulated difference between autilization of one or more transmit opportunities (TXOPs) for atransmission of data from a wireless communication device and a TXOPlimit; a contention window (CW) adjuster configured to adjust a CW valuefor a subsequent transmission from the wireless communication devicebased at least in part on the determining; and an update unit configuredset initial contention window (CWs) such that a ratio between an averageCW and an average sum of the TXOP limit and the accumulated differenceequals a ratio between a minimum CW and the TXOP limit.

The apparatus may implement one or more aspects of the first, second, orthird methods described above.

An apparatus for wireless communications may include means fordetermining a utilization of a transmit opportunity (TXOP) for atransmission of data from a wireless communication device; means fordetermining a difference between the utilization of the TXOP and a TXOPlimit; and means for aggregating the difference with an accumulateddifference between at least one other TXOP and a TXOP limit for theother TXOP.

The apparatus may include means for implementing one or more aspects ofthe first, second, or third methods described above.

An apparatus for wireless communications may include means fordetermining an accumulated difference between a utilization of one ormore transmit opportunities (TXOPs) for a transmission of data from awireless communication device and a TXOP limit; means for adjusting acontention window (CW) value for a subsequent transmission from thewireless communication device based at least in part on the determining;and means for updating the accumulated difference based at least in parton the adjusted CW value.

The apparatus may include means for implementing one or more aspects ofthe first, second, or third methods described above.

An apparatus for wireless communications may include means fordetermining a utilization of a transmit opportunity (TXOP) for atransmission of data from a wireless communication device; means fordetermining a difference between the utilization of the TXOP and a TXOPlimit; means for aggregating the difference with an accumulateddifference between at least one other TXOP and a TXOP limit for theother TXOP; and means for setting initial contention windows (CWs) suchthat a ratio between an average CW and an average sum of the TXOP limitand the accumulated difference equals a ratio between a minimum CW andthe TXOP limit.

The apparatus may include means for implementing one or more aspects ofthe first second, or third methods described above.

A non-transitory computer-readable medium may store instructionsexecutable by a processor to cause at least one device to: determine autilization of a transmit opportunity (TXOP) for a transmission of datafrom a wireless communication device; determine a difference between theutilization of the TXOP and a TXOP limit; and aggregate the differencewith an accumulated difference between at least one other TXOP and aTXOP limit for the other TXOP.

The instructions may be further executable by the processor to cause theat least one device to implement one or more aspects of the first,second, or third methods or apparatuses described above.

A non-transitory computer-readable medium may store instructionsexecutable by a processor to cause at least one device to: determine anaccumulated difference between a utilization of one or more transmitopportunities (TXOPs) for a transmission of data from a wirelesscommunication device and a TXOP limit; adjust a contention window (CW)value for a subsequent transmission from the wireless communicationdevice based at least in part on the determination; and update theaccumulated difference based at least in part on the adjusted CW value.

The instructions may be further executed by the processor to cause theat least one device to implement one or more aspects of the first,second, or third methods or apparatuses described above.

A non-transitory computer-readable medium may store instructionsexecutable by a processor to cause at least one device to: determine autilization of a transmit opportunity (TXOP) for a transmission of datafrom a wireless communication device; determine a difference between theutilization of the TXOP and a TXOP limit; aggregate the difference withan accumulated difference between at least one other TXOP and a TXOPlimit for the other TXOP; and set initial contention windows (CWs) suchthat a ratio between an average CW and an average sum of the TXOP limitand the accumulated difference equals a ratio between a minimum CW andthe TXOP limit.

The instructions may be further executable by the processor to cause theat least one device to implement one or more aspects of the first,second, or third methods or apparatuses described above.

The foregoing has outlined rather broadly the features and technicaladvantages of examples according to the disclosure in order that thedetailed description that follows may be better understood. Additionalfeatures and advantages will be described hereinafter. The conceptionand specific examples disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present disclosure. Such equivalent constructions do notdepart from the spirit and scope of the appended claims. Features whichare believed to be characteristic of the concepts disclosed herein, bothas to their organization and method of operation, together withassociated advantages will be better understood from the followingdescription when considered in connection with the accompanying figures.Each of the figures is provided for the purpose of illustration anddescription only, and not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentdisclosure may be realized by reference to the following drawings. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 shows a diagram that illustrates an example of a wireless localarea network (WLAN) that supports power conservation modes according tovarious examples;

FIG. 2 shows a diagram that illustrates an example of data transmissionbetween an AP and a station according to various examples;

FIG. 3 shows a diagram that illustrates another example of datatransmission between an AP and a station according to various examples;

FIG. 4 is a flowchart of an example of operations related to adjusting acontention window for wireless channel access according to variousexamples;

FIGS. 5A-5C show a block diagrams that illustrate examples of anarchitecture for adjusting contention windows according to variousexamples;

FIG. 6 shows a block diagram that illustrates an example of a stationarchitecture according to various examples;

FIG. 7 shows a block diagram that illustrates an example of an AParchitecture according to various examples;

FIG. 8 is a flowchart of an example of a method for contention windowadjustment in a wireless communication system according to variousexamples;

FIG. 9 is a flowchart of an example of another method for contentionwindow adjustment in a wireless communication system according tovarious examples;

FIG. 10 is a flowchart of an example of yet another method forcontention window adjustment in a wireless communication systemaccording to various examples; and

FIG. 11 is a flowchart of an example of a method for dynamic control ofcontention windows in a wireless communication system according tovarious examples.

DETAILED DESCRIPTION

Described examples are directed to methods, systems, devices, andapparatuses for accessing a wireless channel in a wirelesscommunications network that may enhance network utilization and powerconservation through efficient transmissions of information between anAP and a station. Efficient use of transmit opportunities (TXOPs) may beenhanced through adjustment of contention window (CW) backoff timevalues to compensate for one or more TXOPs that may exceed a TXOP limitthat is set by the network. A CW value may be increased, for example, toprovide other devices in the network with a fair opportunity for networkaccess based at least in part on one or more TXOPs that exceed the TXOPlimit. Allowing one or more transmissions to exceed a TXOP limit mayprovide enhanced efficiency as compared to having multipletransmissions, each with related overhead, that are each within the TXOPlimit.

Compensation may be achieved, according to certain examples, throughdetermination of a utilization of a transmit opportunity (TXOP), anddetermination of a difference between the utilization of the TXOP and aTXOP limit. The difference between the utilization of the TXOP and TXOPlimit may be aggregated with an accumulated difference between at leastone TXOP and the TXOP limit. Based at least in part on the accumulateddifference, a contention window (CW) value may be adjusted for asubsequent transmission from the wireless communication device. Theaccumulated difference may then be adjusted based at least in part onthe adjusted CW value. Less than fully utilized TXOPs may be used tocompensate for later TXOPs that may exceed the TXOP limit. Compensationof CW values may be through linear or exponential compensation,according to various examples.

The channel access techniques presented herein are generally describedin connection with WLANs for simplicity. A WLAN (or Wi-Fi network) mayrefer to a network that is based at least in part on the protocolsdescribed in the various IEEE 802.11 standards (e.g., 802.11a/g,802.11n, 802.11ac, 802.11ah, etc.). The same or similar techniques,however, may be used for various other wireless communications systemssuch as cellular wireless systems, peer-to-peer wireless communications,ad hoc networks, satellite communications systems, and other systems.The terms “system” and “network” may be used interchangeably.

Thus, the following description provides examples, and is not limitingof the scope, applicability, or configuration set forth in the claims.Changes may be made in the function and arrangement of elementsdiscussed without departing from the spirit and scope of the disclosure.Various examples may omit, substitute, or add various procedures orcomponents as appropriate. For instance, the methods described may beperformed in an order different from that described, and various stepsmay be added, omitted, or combined. Also, features described withrespect to certain examples may be combined in other examples.

Referring first to FIG. 1, a WLAN or Wi-Fi network 100 is shown that isconfigured to provide enhanced network utilization. The WLAN 100includes an AP 105 and multiple associated stations 115. In thisexample, there are shown seven (7) stations or STAs 115, which areidentified as STA_1, STA_2, STA_3, STA_4, STA_5, STA_6, and STA_7. TheWLAN 100, however, may have more or fewer stations 115 than those shownin FIG. 1 since the number shown is simply for illustrative purposes.The AP 105 and the associated stations 115 may represent a basic serviceset (BSS). The various stations 115 in the BSS are able to communicatewith one another through the AP 105. Also shown is a coverage area 120of the AP 105, which may represent a basic service area (BSA) of theWLAN 100. Although not shown in FIG. 1, the BSS associated with the WLAN100 is typically connected to a wired or wireless distribution system(DS) that allows multiple APs to be connected in an extended serviceset.

The AP 105 is configured to communicate bi-directionally with each ofthe stations 115 using transmissions 130. The transmissions 130 mayinclude downlink transmissions (e.g., beacon frames) that are sent fromthe AP 105 to a station 115 as well as uplink transmissions of dataframes that are sent from a station 115 to the AP 105, which arereferred to as transmission opportunities (TXOPs). Different stations115 transmitting, using the wireless medium, simultaneously may resultin collisions in transmissions, a large number of which may degrade theefficiency of the network 100. Following a TXOP, a station 115 waits fora backoff period prior to attempting to another transmission. Thebackoff period may be set based at least in part on a contention window(CW) value that is defined for the network 100, as a value between aminimum CW value (CWmin) and a maximum CW value (CWmax), as will bedescribed in more detail below. Collisions between stations 115 may beresolved according to contention mechanisms that result in the stations115 attempting retransmissions following backoff periods that increasefollowing each detection of a collision. A station 115 that sends manyshort TXOPs separated by a backoff may have a higher contention activitythan a station 115 that groups traffic into longer but fewer TXOPs. Thelatter may be implemented according to various techniques described inmore detail below, resulting in relatively longer TXOPs that may exceedan established TXOP limit, and which may be compensated throughincreased contention window (CW) backoff values. This may result inenhanced network efficiency through reduced relative overhead, as wellas reduced power consumption of both the stations 115 and AP 105.

The backoff counter is determined as a random integer drawn from auniform distribution over the interval [0,CW]. The CW size, according tovarious examples, may be calculated according to different techniques inorder to enhance network efficiency while maintaining required QoS foran access class, as will be described in further detail below. If thechannel becomes busy during a backoff process, the backoff counter issuspended. When the channel becomes idle again, and stays idle for anextra distributed coordination function (DCF) interframe space (DIFS)time interval, the backoff process resumes with the suspended backoffcounter value.

For each successful reception of a frame, the receiving stationimmediately acknowledges by sending an acknowledgement (ACK) frame. TheACK frame is transmitted after a short interframe space (SIFS), which isshorter than the DIFS, and thus does not result in other stationsattempting to gain access to the medium. Other stations resume thebackoff process after the DIFS idle time. If an ACK frame is notreceived after the data transmission, the frame is retransmitted afteranother random backoff. Following the expiration of the backoff counter,station 115 may transmit a request to send (RTS). In the event thatthere is no collision with another station 115, the AP 105 may send aclear to send (CTS) indication to the station 115. Station 115 may thentransmit data to the AP 105, and the process then repeats. The CW may bereset after a successful TXOP to a minimum CW size (CWmin), where CWminis the minimum contention window for the access category (AC) for whichthe TXOP was obtained. The contention window that is used after asuccessful TXOP is referred to as the initial CW.

Fairness in channel access may be maintained through adjustment of theinitial CW. For example, 802.11b transmissions may consume a relativelyhigh amount of airtime because even a single data MPDU can occupy themedium for about 12 ms, which is a significant amount of time relativeto an OFDM transmission of 2 ms, for example. Another potential sourceof channel access unfairness may be caused by an aggregated MPDU(A-MPDU). An A-MPDU at a low rate may cause a very long transmission,similar to an 802.11b transmission. In order to restore channel accessfairness, an EDCA TXOP limit can be set to a non-zero value, thuslimiting transmissions to a maximum duration established by the TXOPlimit. However, in certain cases it may be beneficial to extend certaintransmissions beyond the TXOP limit, in order to capitalize on freshsounding information or to amortize TXOP related overhead such asRTS/CTS protection and acknowledgements.

According to certain examples, TXOPs that exceed the TXOP limit can beexchanged for a longer average backoff, thus offsetting the excesschannel usage time by an increased time period during which the station115 does not attempt channel access. The compensation, according toexamples, may be such that the average amount of airtime between devicesthat do and those that do not exceed the TXOP limit is about the same,on average. A station 115 may keep track of the excess TXOP time fortransmissions that exceed the TXOP limit. For example, after each TXOP,the time the TXOP takes beyond the TXOP limit is added to the excessTXOP time. Additionally or alternatively, before a TXOP, the time theTXOP will take beyond the TXOP limit may be added to the excess TXOPtime. Increasing the CW value may include exponentially increasing theCW value when the relative excess is greater than a predetermined value,such as when the relative excess corresponds to an integer multiple ofthe TXOP limit, in which case the CW value may be adjusted by increasingthe CW value by an exponential factor that is based at least in part onthe integer multiple. Adjusting the CW value may include linearlyincreasing the CW value when the relative excess is greater than apredetermined value. Various examples of CW adjustment based at least inpart on TXOP times will be described with respect to FIGS. 2-11.

With reference now to FIG. 2, an example 200 of transmissions between astation and an AP, such as between a station 115 and AP 105 of FIG. 1,according to various examples is described. Station and AP may implementRTS/CTS techniques, and may adjust a CW value based at least in part onutilization of one or more TXOPs. Alternatively, a station may initiatea TXOP directly, and in the absence of an ACK from the AP following afirst frame may determine that a collision has occurred. In FIG. 2, theAP sends a CTS 205 to station. After a SIFS, 210, the station mayinitiate TXOP 215 to transmit data. A TXOP limit 220 may be establishedby the AP, and the TXOP 215 in this example exceeds the TXOP limit 220by an amount Tdiff-1 225.

As mentioned above, in certain examples TXOPs that exceed the TXOP limitcan be exchanged for a longer average backoff, which may be accomplishedthrough increasing a CW value. The compensation provided, in certainexamples, may be such that the average amount of airtime between devicesthat do exceed the TXOP limit 220 and those that do not exceed the TXOPlimit 220 is about the same, on average. To this end, in examples, theSTA may keep track of the excess TXOP times through accumulation ofmultiple Tdiff values from multiple TXOPs. A CW may be adjusted when anaccumulated excess TXOP time exceeds a certain value.

Continuing with the example of FIG. 2, the station waits a backoff timebased at least in part on CWmin 230, and sends RTS 235. Following SIFS210, in this example, access point sends CTS 205, and the stationinitiates TXOP 240 following another SIFS 210. Again, in this example,TXOP 240 exceeds the TXOP limit 220 by an amount Tdiff-2 245, and thestation may aggregate Tdiff-1 225 and Tdiff-2 245 to determine anaccumulated excess TXOP time. Continuing with the example of FIG. 2,this process repeats when the station initiates TXOP 250 which exceedsthe TXOP limit 220 by an amount Tdiff-3 255. The accumulated excess TXOPtime may be large enough to initiate an adjusted CW 260, in which theinitial CW value is increased in order to compensate for the accumulatedexcess TXOP time. The adjustment of the CW value may be accomplishedusing one of a number of available techniques. The CW value may belinearly scaled based at least in part on the amount of excess TXOP timerelative to the TXOP limit. The CW value may also be exponentiallyincreased based at least in part on the amount of excess TXOP timerelative to the TXOP limit.

If the CW value is exponentially increased based at least in part on theamount of excess TXOP time relative to the TXOP limit, the CW value maybe determined based at least in part on a number of determinations. Suchexponential increases for CW values may be used, for example, in systemswhere CW values are set according to 2^(X)−1 (e.g., CW values may be 0,3, 7, 15, 31, 53, and so on). Initially, an amount of relative excessTXOP time may be determined based at least in part on the accumulatedexcess TXOP time and the TXOP limit according to the equation:

$\begin{matrix}{{{relative}\mspace{14mu} {excess}\mspace{14mu} {TXOP}\mspace{14mu} {time}} = {\frac{{excess}\mspace{14mu} {TXOP}\mspace{14mu} {time}}{{TXOP}\mspace{14mu} {limit}}.}} & ( {{Eq}.\mspace{14mu} 1} )\end{matrix}$

An order of the excess TXOP time may then be determined according to theequation:

excess TXOP order=floor(log₂(relative excess TXOP time+1),1)  (Eq. 2).

The CW for the initial backoff following each TXOP may then bedetermined according to the equation:

adjusted CW=(CWmin+1)×2^((excess TXOP order)−1)  (Eq. 3).

After the adjustment of the CW, the excess TXOP time may be updatedaccording to the equation:

excess TXOP time=excess TXOP time−(2^((excess TXOP order)) ×TXOPlimit)−TXOP limit  (Eq. 4).

Tables 1-3 provide a number of numerical examples based at least in parton different values of CWmin, different TXOP limits, and differentrealized TXOP times. In Table 1, CWmin is set to 15 slots, the TXOPlimit is set to 2 ms, and each realized TXOP is 2.5 ms. Thus, each TXOPexceeds the TXOP limit by 25%, resulting in a relative excess TXOP timeof 0.25 for each TXOP, according to Eq. 1. As discussed above, theexcess TXOP time may be accumulated and thus every fourth TXOP theaccumulated excess TXOP corresponds to a relative excess TXOP time of1.0, which would increase the excess TXOP order according to Eq. 2. Theadjusted CW value is determined for each TXOP according to Eq. 3, andthus increases by an order of magnitude every fourth TXOP in thisexample. Following a CW adjustment, the excess TXOP time is updatedaccording to Eq. 4, and in the example of Table 1 is reset to zerofollowing every fourth TXOP.

TABLE 1 CWmin TXOP realized excess relative excess CW for next nextexcess TXOP# (slots) limit TXOP TXOP time TXOP time order initial TXOPTXOP time 1 15 2 2.5 0.5 0.25 0 15 0.5 2 15 2 2.5 1.0 0.50 0 15 1.0 3 152 2.5 1.5 0.75 0 15 1.5 4 15 2 2.5 2.0 1.00 1 31 0.0 5 15 2 2.5 0.5 0.250 15 0.5 6 15 2 2.5 1.0 0.50 0 15 1.0 7 15 2 2.5 1.5 0.75 0 15 1.5 8 152 2.5 2.0 1.00 1 31 0.0 9 15 2 2.5 0.5 0.25 0 15 0.5 10 15 2 2.5 1.00.50 0 15 1.0 11 15 2 2.5 1.5 0.75 0 15 1.5

In Table 2, CWmin is again set to 15 slots; the TXOP limit is set to 2ms; and each realized TXOP is 2.2 ms. Thus, each TXOP exceeds the TXOPlimit by 10%, resulting in a relative excess TXOP time of 0.10 for eachTXOP, according to Eq. 1. Thus, in every tenth TXOP the accumulatedexcess TXOP corresponds to, in this example, a relative excess TXOP timeof 1, which would increase the excess TXOP order according to Eq. 2. Theadjusted CW value is determined for each TXOP according to Eq. 3, andthus increases by an order of magnitude every tenth TXOP in thisexample. Following a CW adjustment, the excess TXOP time is updatedaccording to Eq. 4, and in the example of Table 1 is reset to zerofollowing every tenth TXOP.

TABLE 2 CWmin TXOP realized excess relative excess CW for next nextexcess TXOP# (slots) limit TXOP TXOP time TXOP time order initial TXOPTXOP time 1 15 2 2.2 0.2 0.10 0 15 0.2 2 15 2 2.2 0.4 0.20 0 15 0.4 3 152 2.2 0.6 0.30 0 15 0.6 4 15 2 2.2 0.8 0.40 1 15 0.8 5 15 2 2.2 1.0 0.500 15 1.0 6 15 2 2.2 1.2 0.60 0 15 1.2 7 15 2 2.2 1.4 0.70 0 15 1.4 8 152 2.2 1.6 0.80 0 15 1.6 9 15 2 2.2 1.8 0.90 0 15 1.8 10 15 2 2.2 2.01.00 1 31 0.0 11 15 2 2.2 0.2 0.10 0 15 0.2

In Table 3, CWmin is again set to 15 slots; the TXOP limit is set to 2ms; however, each realized TXOP is 5.0 ms. Thus, each TXOP exceeds theTXOP limit by 150%, resulting in a relative excess TXOP time of 1.5 foreach TXOP, according to Eq. 1. Thus, for the first through third TXOPsthe accumulated excess TXOP corresponds to an increase in TXOP order of1.0, according to Eq. 2, with every fourth TXOP having an excess TXOPorder increased to 2.0. Thus, the adjusted CW value is 31 (relative toCWmin of 15), with every fourth TXOP having an adjusted CW value of 63,according to Eq. 3. Following each CW adjustment, the excess TXOP timeis updated according to Eq. 4, as shown in the left-most column of Table3.

TABLE 3 CWmin TXOP realized excess relative excess CW for next nextexcess TXOP# (slots) limit TXOP TXOP time TXOP time order initial TXOPTXOP time 1 15 2 5.0 3.0 1.5 1 31 1.0 2 15 2 5.0 4.0 2.0 1 31 2.0 3 15 25.0 5.0 2.5 1 31 3.0 4 15 2 5.0 6.0 3.0 2 63 0.0 5 15 2 5.0 3.0 1.5 1 311.0 6 15 2 5.0 4.0 2.0 1 31 2.0 7 15 2 5.0 5.0 2.5 1 31 3.0 8 15 2 5.06.0 3.0 2 63 0.0 9 15 2 5.0 3.0 1.5 1 31 1.0 10 15 2 5.0 4.0 2.0 1 312.0 11 15 2 5.0 5.0 2.5 1 31 3.0

As discussed above, CW values may be scaled according to a linearincrease of the initial CW value, and a station may monitor the excessTXOP time (if any) for each TXOP. After each TXOP, the TXOP utilizationis determined and a difference in TXOP time relative to the TXOP limitis aggregated to an accumulated excess TXOP time, similarly as discussedabove. At each initial backoff, an adjusted CW value may be determinedand the excess TXOP time may be updated based at least in part on theadjusted CW value. Initially, an adjusted CW value is determinedaccording to the following equation:

$\begin{matrix}{{{adjusted}\mspace{14mu} {CW}} = {{{floor}( {{{CW}\; \min \times ( {1 + \frac{{excess}\mspace{14mu} {TXOP}\mspace{14mu} {time}}{{TXOP}\mspace{14mu} {limit}}} )},1} )}.}} & ( {{Eq}.\mspace{14mu} 5} )\end{matrix}$

After the adjustment of the CW, the excess TXOP time may be updatedaccording to the equation:

$\begin{matrix}{{{excess}\mspace{14mu} {TXOP}\mspace{14mu} {time}} = {{{excess}\mspace{14mu} {TXOP}\mspace{14mu} {time}} - {( {( {\frac{{adj} \cdot {CW}}{{CW}\; \min} - 1} ) \times {TXOP}\mspace{14mu} {limit}} ).}}} & ( {{Eq}.\mspace{14mu} 6} )\end{matrix}$

Tables 4-6 provide a number of numerical examples based at least in parton different values of CWmin, different TXOP limits, and differentrealized TXOP times. In Table 4, CWmin is set to 15 slots; the TXOPlimit is set to 2 ms; and each realized TXOP is 2.5 ms. Thus, in thisexample, each TXOP exceeds the TXOP limit by 25%, resulting in arelative excess TXOP time of 0.25 for each TXOP, according to Eq. 1. Asdiscussed above, the CW value for each TXOP is scaled according to Eq.5, and thus increases relative to CWmin are present for each subsequentTXOP. Following a CW adjustment, the excess TXOP time is updatedaccording to Eq. 6.

TABLE 4 CWmin TXOP realized excess relative excess CW for next nextexcess TXOP# (slots) limit TXOP TXOP time TXOP time initial TXOP TXOPtime 1 15 2 2.5 0.5 0.25 18 0.1 2 15 2 2.5 0.6 0.30 19 0.1 3 15 2 2.50.6 0.28 19 0.0 4 15 2 2.5 0.5 0.27 19 0.0 5 15 2 2.5 0.5 0.25 18 0.1 615 2 2.5 0.6 0.30 19 0.1 7 15 2 2.5 0.6 0.28 19 0.0 8 15 2 2.5 0.5 0.2719 0.0 9 15 2 2.5 0.5 0.25 18 0.1 10 15 2 2.5 0.6 0.30 19 0.1 11 15 22.5 0.6 0.28 19 0.0

In Table 5, CWmin is again set to 15 slots; the TXOP limit is set to 2ms; and each realized TXOP is 2.2 ms. Thus, each TXOP exceeds the TXOPlimit by 10%, resulting in a relative excess TXOP time of 0.10 for eachTXOP, according to Eq. 1. As discussed above, the CW value for each TXOPis scaled according to Eq. 5, and thus increases relative to CWmin arepresent for each subsequent TXOP. Following a CW adjustment, the excessTXOP time is updated according to Eq. 6.

TABLE 5 CWmin TXOP realized excess relative excess CW for next nextexcess TXOP# (slots) limit TXOP TXOP time TXOP time initial TXOP TXOPtime 1 15 2 2.2 0.2 0.10 16 0.1 2 15 2 2.2 0.3 0.13 17 0.0 3 15 2 2.20.2 0.10 16 0.1 4 15 2 2.2 0.3 0.13 17 0.0 5 15 2 2.2 0.2 0.10 16 0.1 615 2 2.2 0.3 0.13 17 0.0 7 15 2 2.2 0.2 0.10 16 0.1 8 15 2 2.2 0.3 0.1317 0.0 9 15 2 2.2 0.2 0.10 16 0.1 10 15 2 2.2 0.3 0.13 17 0.0 11 15 22.2 0.2 0.10 16 0.1

In Table 6, CWmin is again set to 15 slots; and the TXOP limit is set to2 ms; however, each realized TXOP is 5.0 ms. Thus, each TXOP exceeds theTXOP limit by 150%, resulting in a relative excess TXOP time of 1.5 foreach TXOP, according to Eq. 1. As discussed above, the CW value for eachTXOP is scaled according to Eq. 5, and thus increases relative to CWminare present for each subsequent TXOP. Following a CW adjustment, theexcess TXOP time is updated according to Eq. 6.

TABLE 6 CWmin TXOP realized excess relative excess CW for next nextexcess TXOP# (slots) limit TXOP TXOP time TXOP time initial TXOP TXOPtime 1 15 2 5.0 3.0 1.50 37 0.1 2 15 2 5.0 3.1 1.50 38 0.0 3 15 2 5.03.0 1.50 37 0.1 4 15 2 5.0 3.1 1.50 38 0.0 5 15 2 5.0 3.0 1.50 37 0.1 615 2 5.0 3.1 1.50 38 0.0 7 15 2 5.0 3.0 1.50 37 0.1 8 15 2 5.0 3.1 1.5038 0.0 9 15 2 5.0 3.0 1.50 37 0.1 10 15 2 5.0 3.1 1.50 38 0.0 11 15 25.0 3.0 1.50 37 0.1

Adjustments to CW values may be made to the initial CW value, but notsubsequent CW values in the event that a collision occurs. According tothe EDCA backoff rules, the CW may be increased to the next power of 2minus 1 if no response is received to a transmission (e.g., there is acollision). When the initial CW value is selected according to thelogarithmic (Eqs. 1-4) or linear (Eqs. 5-6) compensation techniques,subsequent CW values in the event of a collision may be selected to bethe next power of 2 minus 1 based at least in part on the CWmin value,rather than the adjusted CW value. This may avoid a situation whereretries also compensate for excess TXOP time, which is not neededbecause the initial backoff time already included compensation to adjustfor excess TXOP time.

Various additional techniques may be employed for both the linear andthe logarithmic methods. For example, in some cases a station may checkwhether compensation is required only after every a given number ofTXOPs, or for a given time interval. The given number of TXOPs timeinterval may change per interval, in some examples. The compensation maybe larger in such cases, but long term fairness may still be achievedand require lower processing overhead. Each time the compensation isexecuted, the procedure may be employed as described above. Namely, theexcess TXOP time relative to the TXOP limit is multiplied by CWmin androunded down either to the next integer or to the next power of 2minus 1. The resulting value is used as the CW value for the nextinitial backoff. The resulting CW value relative to CWmin is multipliedby the TXOP limit and subtracted from the excess TXOP time to adjust theaccumulated excess TXOP time to account for the adjustment in the CWvalue.

As discussed above, the excess TXOP time is reduced when an adjusted CWvalue is larger than CWmin. TXOPs that are shorter than the TXOP limitmay be used to compensate excess TXOP time for one or more subsequentTXOPs. FIG. 3 illustrates an example 300 of transmissions between astation and an AP, such as between a station 115 and AP 105 of FIG. 1,according to examples that may employ such dual-compensation techniques.Station and AP may implement RTS/CTS techniques, and may adjust a CWvalue based at least in part on utilization of one or more TXOPs.Alternatively, a station may initiate a TXOP directly, and in theabsence of an ACK from the AP following a first frame may determine thata collision has occurred. In FIG. 3, the AP sends a CTS 305 to station.After a SIFS, 310, the station may initiate TXOP 315 to transmit data.TXOP time 370 may be less than TXOP limit 320, thus resulting in aTdiff-4 325 that indicates the TXOP utilization was less than an allowedTXOP utilization. The station waits a backoff time based at least inpart on CWmin 330, and sends RTS 335, and repeats the process.

As mentioned above, TXOPs that exceed the TXOP limit may be exchangedfor a longer average backoff, which may be accomplished throughincreasing a CW value. In a dual compensation example such as in FIG. 3,TXOPs that utilize less than the TXOP limit may be used to compensatesubsequent TXOPs that exceed the TXOP limit. In FIG. 3, TXOP 345 mayhave a TXOP time that exceeds TXOP limit 320, resulting in Tdiff-5 355.Tdiff-5 355 may be aggregated with Tdiff-4 325, and the result may bethat a subsequent CW value may not require adjustment, and a backoffbased at least in part on CWmin 330 may follow TXOP 345 even though theTXOP time 350 of TXOP 345 exceeded TXOP limit 320. TXOP 360 may fullyutilize TXOP limit 320 resulting in no difference value, and CWmin 365may follow TXOP 360. Similarly as discussed above, the compensationprovided may be such that the average amount of airtime between devicesthat do exceed the TXOP limit 320 and those that do not exceed the TXOPlimit 320 is about the same, on average. To this end, in examples, thestation may keep track of the excess TXOP times through accumulation ofmultiple Tdiff values from multiple TXOPs. A CW may also be adjustedwhen an accumulated excess TXOP time exceeds a certain value.

Excess TXOP time for dual compensation may be maintained by determininga Tdiff for each TXOP, according to the following equation:

Tdiff=TXOP time−TXOP limit  (Eq. 7).

The value of Tdiff may be aggregated with existing accumulated excessTXOP time. The excess TXOP time may be initialized at 0, and a maxoperation may be used to provide that the excess TXOP time is neversmaller than 0, such as according to the following equation:

Texcess=max(Texcess+Tdif,0)  (Eq. 8).

Table 7 provides a numerical example in which the TXOP limit is set to 2ms, and each realized TXOP time is indicated in the right column.

TABLE 7 Dif from excess TXOP TXOP time TXOP limit time 1.5 −0.5 0 1.2−0.8 0 2.8 0.8 0.8 2.9 0.9 1.7 3.1 1.1 2.8 1.2 −0.8 2 1.2 −0.8 1.2 1.5−0.5 0.7 0.8 −1.2 0 1.8 −0.2 0

In addition to compensation through the TXOP time, the excess TXOP timemay also be compensated by setting a higher CW for an initial TXOP. Therelative excess may be determined according to the following equation:

relativeExcess=Texcess/TXOP limit  (Eq. 9).

Therefore, the extra CW may be determined according to:

extraCW=CWmin×relativeExcess  (Eq. 10).

The initial CW value may then be adjusted according to:

Adjusted CW=CWmin+extraCW  (Eq. 11).

The adjusted CW value may be rounded to an integer value correspondingto a number of slots for the CW value. Next, a deduction to the excessTXOP time due to the extra CW may be determined according to:

TExcessDeduction=TXOP limit*extraCW/CWmin  (Eq. 12).

In deployments that require a CW value to be a power of 2 minus 1, thelog 2 may be taken from the adjusted CW, rounded down to the next lowerinteger, and applied as a power of 2 minus 1, according to:

log(adjusted CW)=log 2(adjusted CW+1)  (Eq. 13).

The value from Eq. 13 may be rounded down to the nearest integer. Thus,a second adjusted CW (CWadj2) for such cases, as power of 2 minus 1 maybe determined according to:

CWadj2=2^(log(Adjusted CW))−1  (Eq. 14).

The deduction to the excess TXOP time due to the adjusted CW value maybe determined according to:

$\begin{matrix}{{TExcessDeduction} = {{TXOP}\mspace{14mu} {limit} \times {\frac{{{CWadj}\; 2} - {{CW}\; \min}}{{CW}\; \min}.}}} & ( {{Eq}.\mspace{14mu} 15} )\end{matrix}$

The differences between the adjusted CW and CWadj2 for examples that dolinear versus exponential compensation are illustrated in Table 8 below.

TABLE 8 Adj. Log2(Adj. rounded CW CW + 1) down CWadj2 1 1.00 1 1 2 1.581 1 3 2.00 2 3 4 2.32 2 3 5 2.58 2 3 6 2.81 2 3 7 3.00 3 7 8 3.17 3 7 93.32 3 7 10 3.46 3 7 11 3.58 3 7 12 3.70 3 7 13 3.81 3 7 14 3.91 3 7 154.00 4 15 16 4.09 4 15 17 4.17 4 15 18 4.25 4 15 19 4.32 4 15 20 4.39 415 21 4.46 4 15 22 4.52 4 15 23 4.58 4 15 24 4.64 4 15 25 4.70 4 15 264.75 4 15 27 4.81 4 15 28 4.86 4 15 29 4.91 4 15 30 4.95 4 15 31 5.00 531 32 5.04 5 31 33 5.09 5 31 34 5.13 5 31 35 5.17 5 31 36 5.21 5 31 375.25 5 31 38 5.29 5 31 39 5.32 5 31 40 5.36 5 31 41 5.39 5 31 42 5.43 531 43 5.46 5 31 44 5.49 5 31 45 5.52 5 31 46 5.55 5 31 47 5.58 5 31 485.61 5 31 49 5.64 5 31 50 5.67 5 31 51 5.70 5 31 52 5.73 5 31 53 5.75 531 54 5.78 5 31 55 5.81 5 31 56 5.83 5 31 57 5.86 5 31 58 5.88 5 31 595.91 5 31 60 5.93 5 31 61 5.95 5 31 62 5.98 5 31 63 6.00 6 63 64 6.02 663 65 6.04 6 63 66 6.07 6 63 67 6.09 6 63 68 6.11 6 63 69 6.13 6 63 706.15 6 63

It is also possible to determine the Texcess values at which theadjusted CW jumps to the next power of 2 minus 1, as illustrated inTable 9.

TABLE 9 CWmin TXOPlimit CWadj2 TExcessDeduction 15 2 15 0 15 2 31 2.1 152 63 6.4 15 2 127 14.9 15 2 255 32.0 15 2 511 66.1 15 2 1023 134.4 15 22047 270.9As may be observed from Eqs. 9-15 and from Table 9, once Texcess is inthe range between 2.1 and 6.4 ms, a compensation occurs by a CW equal to31. Similarly, a Texcess between 6.4 and 14.9 is compensated by a CWequal to 63, and so on.

Techniques are provided that allow for obtaining excess TXOP time inadvance by setting an initial CW value to be larger than CWmin prior toinitiating a TXOP that exceeds the TXOP limit. The amount of excess TXOPtime obtained by setting a larger initial CW value may be determined,for example, according to:

Texcess=Texcess+TXOP limit×(initial CW−Cwmin)/CWmin  (Eq. 16).

For example, an initial CW may be set to 31 for an initial backoff whenCWmin is 15. Such an adjustment in the initial CW may gain 2.1 ms ofexcess TXOP time, which is the same value as shown in the second row ofTable 9 for TExcessDeduction. Such excess TXOP time may be deducted fromTexcess, after which Texcess can be filled again by one or more initialCWs that are larger than CWmin. Texcess may also be filled by TXOPs thatare shorter than the TXOP limit. The accumulated time less than the TXOPlimit can be added to Texcess, in a similar manner as described above.

With reference now to FIG. 4, a flow diagram of a method 400 foradjusting a CW size at a station is discussed in accordance with variousexamples. The method 400 may be implemented using, for example, thestations 115 of FIG. 1, station 115 of FIG. 7 or devices of FIGS. 5Athrough 5C, discussed below. At block 405, the station transmits RTSframe. At block 410, the station determines if CTS is received. If CTSis not received, the station increases the CW according to usualcollision avoidance techniques, up to a limit of CWmax, as indicated atblock 415. The station waits for a backoff counter that is set based atleast in part on the CW to expire, as indicated at block 420, andoperations are continued at block 405. If the station does receive aCTS, it transmits data to the AP, as indicated at block 425. At block430, the station determines a utilization of the TXOP. TXOP utilizationmay be determined based at least in part on a TXOP limit duration ascompared to a duration of data transmitted at block 425 (e.g., Tdiff).TXOP utilization may also be determined based at least in part on anamount of data transmitted during the TXOP as compared to a theoreticalmaximum amount of data that could be transmitted during the TXOP.

At block 435, the difference in TXOP times may be aggregated with anaccumulated difference. At block 440, it is determined if the relativeexcess of the accumulated difference requires a CW adjustment. Such adetermination may be made according to one or more of the techniquesdescribed above. If no CW value adjustment is required, the CW value isset to CWmin, as indicated at block 445, and the operations of block 420are repeated. If a CW value adjustment is determined to be necessary,the CW value may be adjusted as indicated at block 450. Such a CWadjustment may be a linear CW adjustment, or an exponential CWadjustment, and may be determined according to the techniques describedabove, for example. At block 455, the accumulated difference in TXOPtimes may be updated based at least in part on the adjusted CW. Such anupdate to the accumulated difference may be determined according to thetechniques described above, for example. Following the update of theaccumulated difference, the operations of block 420 are repeated, withthe backoff counter set according to the adjusted CW from block 450.

With reference now to FIG. 5A, a block diagram 500 illustrates a device505 that may be used for CW adjustment of various examples. The device505 may be an example of one or more aspects of the APs 105 or stations115 described with reference to FIG. 1, or FIGS. 6-7 as will bedescribed below. The device 505, or portions of it, may also be aprocessor. The device 505 may include a receiver 510, a contentionwindow manager 515, or a transmitter 520. Each of these components maybe in communication with each other. The device 505, through thereceiver 510, the contention window manager 515, or the transmitter 520,may be configured to transmit TXOPs according to timing determined basedat least in part on initial or adjusted CWs in order to transmit TXOPshaving durations that may exceed a TXOP limit, similarly as discussedabove with respect to FIGS. 1-4.

With reference now to FIG. 5B, a block diagram 500-a illustrates adevice 530 that may be used for CW adjustment of various examples. Thedevice 530 may be an example of one or more aspects of the APs 105 orstations 115 described with reference to FIG. 1, or FIGS. 6-7 as will bedescribed below. The device 530, or portions of it, may also be aprocessor. The device 530 may include a receiver 510-a, a contentionwindow manager 515-a, or a transmitter 520-a, similarly as describedwith respect to FIG. 5A. Each of these components may be incommunication with each other. The contention window manager 515-a, inthis example, includes a utilization monitor 535 that may monitor theutilization of TXOPs and determine differences between one or moreutilized TXOPs and a TXOP limit. Differences may be determined byutilization monitor 535 according to the techniques described above, forexample. Such differences may be provided to aggregator 540, which mayaggregate differences with an accumulated difference, according totechniques described above with respect to FIGS. 1-4.

With reference now to FIG. 5C, a block diagram 500-b illustrates adevice 550 that may be used for CW adjustment of various examples. Thedevice 550 may be an example of one or more aspects of the APs 105 orstations 115 described with reference to FIG. 1, or FIGS. 6-7 as will bedescribed below. The device 550, or portions of it, may also be aprocessor. The device 550 may include a receiver 510-b, a contentionwindow manager 515-b, or a transmitter 520-b, similarly as describedwith respect to FIGS. 5A and 5B. Each of these components may be incommunication with each other. The contention window manager 515-b, inthis example, includes a utilization monitor 555 that may monitor theutilization of TXOPs and determine differences between one or moreutilized TXOPs and a TXOP limit. Differences may be determined byutilization monitor 555 according to the techniques described above, forexample. A CW adjuster 560 may adjust one or more CW values based atleast in part on TXOP utilization determined by utilization monitor,according to techniques, for example, described above with respect toFIGS. 1-4. Update unit 565 may update accumulated TXOP differences basedat least in part on the adjusted CW value, according to techniques, forexample, described above with respect to FIGS. 1-4.

Turning to FIG. 6, a diagram 600 is shown that illustrates a station115-b configured for CW adjustment based at least in part on TXOPutilization according to various examples. The station 115-b may havevarious other configurations and may be included or be part of apersonal computer (e.g., laptop computer, netbook computer, tabletcomputer, etc.), a cellular telephone, a PDA, a digital video recorder(DVR), an internet appliance, a gaming console, an e-readers, etc. Thestation 115-b may have an internal power supply (not shown), such as asmall battery, to facilitate mobile operation. The station 115-b may bean example of the stations 115 and may implement various operationsdescribed with respect to FIGS. 1-4.

The station 115-b may include a processor 605, a memory 610, atransceiver 625, antennas 630, and a contention window manager 515-c.The contention window manager 515-c may be an example of the contentionwindow manager 515 of FIG. 5A, 5B, or 5C. Each of these components maybe in communication with each other, directly or indirectly, over one ormore buses for example.

The memory 610 may include RAM and ROM. The memory 610 may storecomputer-readable, computer-executable software (SW) code 615 containinginstructions that are configured to, when executed, cause the processor605 to perform various functions described herein for contention windowadjustment. Alternatively, the software code 615 may not be directlyexecutable by the processor 605 but be configured to cause the computer(e.g., when compiled and executed) to perform functions describedherein.

The processor 605 may include an intelligent hardware device, e.g., aCPU, a microcontroller, an ASIC, etc. The processor 605 may processinformation received through the transceiver 625 or to be sent to thetransceiver 625 for transmission through the antennas 630. The processor605 may handle, alone or in connection with the contention windowmanager 620, various aspects for TXOP utilization and CW adjustmentbased at least in part on TXOP utilization and accumulated differencesin TXOP utilization, as described herein.

The transceiver 625 may be configured to communicate bi-directionallywith APs 105 in FIG. 1 or 8. The transceiver 625 may be implemented asone or more transmitters and one or more separate receivers. Thetransceiver 625 may include a modem configured to modulate the packetsand provide the modulated packets to the antennas 630 for transmission,and to demodulate packets received from the antennas 630. While thestation 115-b may include a single antenna, there may be examples inwhich the station 115-b may include multiple antennas 630.

The components of the station 115-b may be configured to implementaspects discussed above with respect to FIGS. 1-5, and those aspects maynot be repeated here for the sake of brevity. Moreover, the componentsof the station 115-b may be configured to implement aspects discussedbelow with respect to FIGS. 8-11, and those aspects may not be repeatedhere also for the sake of brevity.

Turning to FIG. 7, a diagram 700 is shown that illustrates an accesspoint or AP 105-b configured for CW management according to variousexamples. The AP 105-b may be an example of the APs 105 of FIG. 1. TheAP 105-b may include a processor 710, a memory 720, a transceiver 730,antennas 740, and a contention window manager 515-d. The contentionwindow manager 515-d may be an example of the contention window manager515 of FIG. 5A, 5B, or 5C. The AP 105-b may also include one or both ofan AP communications manager 780 and a network communications manager785. Each of these components may be in communication with each other,directly or indirectly, over one or more buses 715.

The memory 720 may include random access memory (RAM) and read-onlymemory (ROM). The memory 720 may also store computer-readable,computer-executable software (SW) code 725 containing instructions thatare configured to, when executed, cause the processor 710 to performvarious functions described herein for CW management and adjustment by astation (e.g., which may be provided to a station, etc.). Alternatively,the software code 725 may not be directly executable by the processor710 but be configured to cause the computer, e.g., when compiled andexecuted, to perform functions described herein.

The processor 710 may include an intelligent hardware device, e.g., acentral processing unit (CPU), a microcontroller, anapplication-specific integrated circuit (ASIC), etc. The processor 710may process information received through the transceiver(s) 730, the APscommunications manager 780, or the network communications manager 785.The processor 710 may also process information to be sent to thetransceiver(s) 730 for transmission through the antenna(s) 740, to theAP communications manager 780, or to the network communications manager785. The processor 710 may handle, alone or in connection with othercomponents, various aspects related to CW management and adjustment asdiscussed above.

The transceiver(s) 730 may include a modem configured to modulate thepackets and provide the modulated packets to the antennas 740 fortransmission, and to demodulate packets received from the antennas 740.The transceiver(s) 730 may be implemented as one or more transmitter(s)and one or more separate receiver(s). The transceiver(s) 730 may beconfigured to communicate bi-directionally, via the antenna(s) 740, withone or more stations 115 as illustrated in FIG. 1, for example. The AP105-b may typically include multiple antennas 740 (e.g., an antennaarray). The AP 105-b may communicate with a core network 705 through thenetwork communications manager 785. The AP 105-b may communicate withother APs, such as the access point 105-i and the access point 105-j,using an AP communications manager 780. The components of the AP 105-bmay be configured to implement aspects discussed above with respect toFIGS. 1-5, and those aspects may not be repeated here for the sake ofbrevity. Moreover, the components of the AP 105-b may be configured toimplement aspects discussed below with respect to FIGS. 8-11 and thoseaspects may not be repeated here also for the sake of brevity.

Turning next to FIG. 8, a flow diagram is described for a method 800 forTXOP utilization determination and aggregation in accordance withvarious examples. The method 800 may be implemented using, for example,the stations 115 of FIG. 1 or 6; APs 105 of FIG. 1 or 7, or devices 505,530, or 550 of FIG. 5A, 5B, or 5C, for example. At block 805, autilization of a transmit opportunity (TXOP) is determined for atransmission of data from a wireless communication device. At block 810,a difference between the utilization of the TXOP and a TXOP limit isdetermined. At block 815, the difference is aggregated with anaccumulated difference between at least one other TXOP and a TXOP limitfor the other TXOP(s).

Turning next to FIG. 9, another flow diagram is described for a method900 for TXOP utilization determination and aggregation in accordancewith various examples. The method 900 may be implemented using, forexample, the stations 115 of FIG. 1 or 6; APs 105 of FIG. 1 or 7, ordevices 505, 530, or 550 of FIG. 5A, 5B, or 5C, for example. At block905, a utilization of a transmit opportunity (TXOP) is determined for atransmission of data from a wireless communication device. At block 910,a difference between the utilization of the TXOP and a TXOP limit isdetermined. At block 915, the difference is aggregated with anaccumulated difference between at least one other TXOP and a TXOP limitfor the other TXOP(s). At block 920, a CW value is adjusted for asubsequent transmission from the wireless communication device based atleast in part on the accumulated difference. At block 925, theaccumulated difference is updated based at least in part on the adjustedCW value.

Turning next to FIG. 10, a flow diagram is described for a method 1000for CW adjustment based at least in part on TXOP utilization inaccordance with various examples. The method 1000 may be implementedusing, for example, the stations 115 of FIG. 1 or 6; APs 105 of FIG. 1or 7, or devices 505, 530, or 550 of FIG. 5A, 5B, or 5C, for example. Atblock 1005, an accumulated difference between a utilization of one ormore transmit opportunities (TXOPs) for a transmission of data from awireless communication device and a TXOP limit is determined. At block1010, a CW value is adjusted for a subsequent transmission from thewireless communication device based at least in part on thedetermination. At block 1015, the accumulated difference is updatedbased at least in part on the adjusted CW value.

Turning next to FIG. 11, another flow diagram is described for a method1100 for CW adjustment based at least in part on TXOP utilization inaccordance with various examples. The method 1100 may be implementedusing, for example, the stations 115 of FIG. 1 or 6; APs 105 of FIG. 1or 7, or devices 505, 530, or 550 of FIG. 5A, 5B, or 5C, for example. Atblock 1105, an accumulated difference between a utilization of one ormore transmit opportunities (TXOPs) for a transmission of data from awireless communication device and a TXOP limit is determined. At block1110, a relative excess between the accumulated difference and a minimumCW value is determined. At block 1015, a CW value is adjusted based atleast in part on the relative excess. At block 1020, the accumulateddifference is updated based at least in part on the adjusted CW value.

The detailed description set forth above in connection with the appendeddrawings describes exemplary examples and does not represent the onlyexamples that may be implemented or that are within the scope of theclaims. The term “exemplary” when used in this description means“serving as an example, instance, or illustration,” and not “preferred”or “advantageous over other examples.” The detailed description includesspecific details for the purpose of providing an understanding of thedescribed techniques. These techniques, however, may be practicedwithout these specific details. Well-known structures and devices areshown in block diagram form in order to avoid obscuring the concepts ofthe described examples.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope and spirit of the disclosure and appended claims. For example,due to the nature of software, functions described above can beimplemented using software executed by a processor, hardware, firmware,hardwiring, or combinations of any of these. Features implementingfunctions may also be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations. Also, as used herein, including in theclaims, “or” as used in a list of items prefaced by “at least one of”indicates a disjunctive list such that, for example, a list of “at leastone of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., Aand B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Throughout this disclosure the term “example” or“exemplary” indicates an example or instance and does not imply orrequire any preference for the noted example. Thus, the disclosure isnot to be limited to the examples and designs described herein but is tobe accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communications, comprising:determining a utilization of a transmit opportunity (TXOP) for atransmission of data from a wireless communication device; determining adifference between the utilization of the TXOP and a TXOP limit;aggregating the difference with an accumulated difference between atleast one other TXOP and a TXOP limit for the other TXOP.
 2. The methodof claim 1, further comprising: adjusting a contention window value fora subsequent transmission from the wireless communication device basedat least in part on the accumulated difference.
 3. The method of claim2, further comprising updating the accumulated difference based at leastin part on the adjusted contention window value.
 4. The method of claim2, wherein adjusting the contention window value comprises: determininga relative excess between the accumulated difference and a minimumcontention window value; and adjusting the contention window value basedat least in part on the relative excess.
 5. The method of claim 4,wherein adjusting the contention window value further comprises: scalingthe minimum contention window value based at least in part on therelative excess.
 6. The method of claim 4, wherein adjusting thecontention window value comprises exponentially increasing thecontention window value when the relative excess is greater than apredetermined value.
 7. The method of claim 6, wherein the predeterminedvalue corresponds to an integer multiple of the TXOP limit.
 8. Themethod of claim 7, wherein exponentially increasing the contentionwindow value comprises increasing the contention window value by anexponential factor that is based on the integer multiple.
 9. The methodof claim 4, wherein increasing the contention window value compriseslinearly increasing the contention window value when the relative excessis greater than a predetermined value.
 10. The method of claim 4,wherein linearly increasing the contention window value comprises:multiplying the relative excess by the minimum contention window value;and rounding down to a next integer contention window value.
 11. Themethod of claim 2, wherein adjusting the contention window valuecomprises: decreasing the contention window value when the accumulateddifference is less than a predetermined value.
 12. The method of claim11, wherein the predetermined value is determined based at least in parton a ratio of the accumulated difference and the TXOP limit.
 13. Themethod of claim 12, wherein decreasing the contention window valuecomprises: multiplying the ratio by a minimum contention window value;and rounding down to a next integer contention window value.
 14. Themethod of claim 2, wherein adjusting the contention window valuecomprises: increasing the contention window value to allow for increasedutilization of a subsequent TXOP relative to the TXOP limit.
 15. Themethod of claim 1, further comprising: determining a second utilizationof a subsequent TXOP during a subsequent transmission of data from thewireless communication device; determining a second difference betweenthe second utilization of the subsequent TXOP and the TXOP limit for thesubsequent TXOP; secondly aggregating the second difference with theaccumulated difference.
 16. An apparatus for wireless communications,comprising: a utilization monitor to determine a utilization of atransmit opportunity (TXOP) for a transmission of data from a wirelesscommunication device and determine a difference between the utilizationof the TXOP and a TXOP limit; an aggregator to aggregate the differencewith an accumulated difference between at least one other TXOP and aTXOP limit for the other TXOP.
 17. The apparatus of claim 16, furthercomprising: a contention window adjuster to adjust a contention windowvalue for a subsequent transmission from the wireless communicationdevice based at least in part on the accumulated difference.
 18. Theapparatus of claim 17, further comprising: an update unit to update theaccumulated difference based at least in part on the adjusted contentionwindow value.
 19. The apparatus of claim 17, wherein: the utilizationmonitor is further to determine a relative excess between theaccumulated difference and a minimum contention window value; and thecontention window adjuster adjusts the contention window value based atleast in part on the relative excess.
 20. The apparatus of claim 19,wherein the contention window adjuster adjusts the contention windowvalue by scaling the minimum contention window value based at least inpart on the relative excess.
 21. The apparatus of claim 19, whereinincreasing the contention window value comprises exponentiallyincreasing the contention window value when the relative excess isgreater than a predetermined value.
 22. The apparatus of claim 21,wherein the predetermined value corresponds to an integer multiple ofthe TXOP limit.
 23. The apparatus of claim 22, wherein exponentiallyincreasing the contention window value comprises increasing thecontention window value by an exponential factor that is based on theinteger multiple.
 24. An apparatus for wireless communications,comprising: means for determining a utilization of a transmitopportunity (TXOP) for a transmission of data from a wirelesscommunication device; means for determining a difference between theutilization of the TXOP and a TXOP limit; means for aggregating thedifference with an accumulated difference between at least one otherTXOP and a TXOP limit for the other TXOP.
 25. The apparatus of claim 24,further comprising: means for adjusting a contention window value for asubsequent transmission from the wireless communication device based atleast in part on the accumulated difference.
 26. The apparatus of claim25, further comprising means for updating the accumulated differencebased at least in part on the adjusted contention window value.
 27. Theapparatus of claim 25, wherein the means for adjusting the contentionwindow value comprises: means for determining a relative excess betweenthe accumulated difference and a minimum contention window value; andwherein the contention window value is adjusted based at least in parton the relative excess.
 28. The apparatus of claim 27, wherein the meansfor adjusting the contention window value further comprises: means forscaling the minimum contention window value based at least in part onthe relative excess.
 29. A non-transitory computer-readable mediumstoring instructions executable by a processor to cause at least onedevice to: determine a utilization of a transmit opportunity (TXOP) fora transmission of data from a wireless communication device; determine adifference between the utilization of the TXOP and a TXOP limit;aggregate the difference with an accumulated difference between at leastone other TXOP and a TXOP limit for the other TXOP.
 30. Thenon-transitory computer-readable medium of claim 29, wherein theinstructions are further executable by the processor to cause the atleast one device to: adjust a contention window value for a subsequenttransmission from the wireless communication device based at least inpart on the accumulated difference.